Dynamics of Glassy Systems: Evaluation of the Dyre Shoving Model

Understanding the dynamic behavior of glass-forming systems remains one of the major challenges of condensed matter science. One model for the structural or alpha-relaxation behavior of such materials is the shoving model of Dyre, in which the physics involves molecules 'shoving' the neighbors, which leads to a temperature dependent activation energy and gives a super-Arrhenius, but non-diverging (with temperature) relaxation time or viscosity. We have successfully evaluated this model using literature data for m-toluidine near to the glass transition temperature and by fitting the dynamic data using either the so-called KWW function or the BSW function. In our findings, it appears that the BSW fit to the data supports the shoving model and its postulate that the temperature dependent activation energy is related to a temperature dependent zero time or infinite frequency modulus. On the other hand, the KWW model gives temperature independent high frequency or short time modulus, with the result that this form of the relaxation dynamics is not consistent with the shoving model. The significance of these results is discussed.